+1 for jdrom17.
IMO if you really, really want to do a budget build, get one of those low-end cases that come with 450/500W PSU's, rather than spend over $50 for a 400W alone. Yeah yeah, I know there's the quality issue with the OEM PSU's already. However, I've bought and built multiple machines using those PSU's, and none have ever failed on me. Never. You'd probably save at least $50 right there, put it towards...a better mobo? GPU?